Document WO 2007/127451 describes a refill of this type, which attaches by magnetic attraction to the inside face of the spine of a protective cover. The spine of the refill described in this document comprises a magnetic element which can stiffen the binding of the pad of pages and make it more difficult to open the pages. This difficulty in opening the pages may lead the user to force them open by pressing on the central portion of the refill, which may damage the refill.